# Homework Help: Total dipole moment

1. Oct 17, 2012

### hansbahia

1. The problem statement, all variables and given/known data

A spherical sheet of radius a has surface-charge density which depends on the polar angle θ according to the formula

σ(θ)=σ0+σ1cos(θ)

Find the total dipole moment

2. Relevant equations
pz=∫(dQ)z
z=rcosθ

3. The attempt at a solution

I calculated the 1st dipole moment
pz=∫∫d∅dθσ0a^3sinθcos^2θ
pz=4/3pi*a^3σ0

I'm not understanding the question, "total" dipole moment?

2. Oct 20, 2012

### gabbagabbahey

When you don't understand a term, the most logical thing to do is to look it up (first try looking in your textbook & notes, and if it isn't there, then try Google, and finally just ask your instructor for clarification).

Total dipole moment just means the electric dipole moment of the entire distribution (the full vector form, not just the z-component that you get from the 2 relevant equations you posted).

3. Oct 25, 2012

### hansbahia

Thanks, I figured out. I had to integrate from 0 to pi

4. Oct 25, 2012

### gabbagabbahey

But do you see why the x- and y-components of the dipole moment are zero here? Getting the right answer is not the same as solving the problem.